Revert "btrfs: compression: drop kmap/kunmap from zstd"

This reverts commit bbaf9715f3f5b5ff0de71da91fcc34ee9c198ed8.

The kmaps in compression code are still needed and cause crashes on
32bit machines (ARM, x86). Reproducible eg. by running fstest btrfs/004
with enabled LZO or ZSTD compression.

Example stacktrace with ZSTD on a 32bit ARM machine:

  Unable to handle kernel NULL pointer dereference at virtual address 00000000
  pgd = c4159ed3
  [00000000] *pgd=00000000
  Internal error: Oops: 5 [#1] PREEMPT SMP ARM
  Modules linked in:
  CPU: 0 PID: 210 Comm: kworker/u2:3 Not tainted 5.14.0-rc79+ #12
  Hardware name: Allwinner sun4i/sun5i Families
  Workqueue: btrfs-delalloc btrfs_work_helper
  PC is at mmiocpy+0x48/0x330
  LR is at ZSTD_compressStream_generic+0x15c/0x28c

  (mmiocpy) from [<c0629648>] (ZSTD_compressStream_generic+0x15c/0x28c)
  (ZSTD_compressStream_generic) from [<c06297dc>] (ZSTD_compressStream+0x64/0xa0)
  (ZSTD_compressStream) from [<c049444c>] (zstd_compress_pages+0x170/0x488)
  (zstd_compress_pages) from [<c0496798>] (btrfs_compress_pages+0x124/0x12c)
  (btrfs_compress_pages) from [<c043c068>] (compress_file_range+0x3c0/0x834)
  (compress_file_range) from [<c043c4ec>] (async_cow_start+0x10/0x28)
  (async_cow_start) from [<c0475c3c>] (btrfs_work_helper+0x100/0x230)
  (btrfs_work_helper) from [<c014ef68>] (process_one_work+0x1b4/0x418)
  (process_one_work) from [<c014f210>] (worker_thread+0x44/0x524)
  (worker_thread) from [<c0156aa4>] (kthread+0x180/0x1b0)
  (kthread) from [<c0100150>]

Link: https://lore.kernel.org/all/CAJCQCtT+OuemovPO7GZk8Y8=qtOObr0XTDp8jh4OHD6y84AFxw@mail.gmail.com/
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=214839
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/zstd.c b/fs/btrfs/zstd.c
index 56dce9f..f06b680 100644 (file)
--- a/fs/btrfs/zstd.c
+++ b/fs/btrfs/zstd.c
@@ -399,7 +399,7 @@ int zstd_compress_pages(struct list_head *ws, struct address_space *mapping,
 
        /* map in the first page of input data */
        in_page = find_get_page(mapping, start >> PAGE_SHIFT);
-       workspace->in_buf.src = page_address(in_page);
+       workspace->in_buf.src = kmap(in_page);
        workspace->in_buf.pos = 0;
        workspace->in_buf.size = min_t(size_t, len, PAGE_SIZE);
 
@@ -411,7 +411,7 @@ int zstd_compress_pages(struct list_head *ws, struct address_space *mapping,
                goto out;
        }
        pages[nr_pages++] = out_page;
-       workspace->out_buf.dst = page_address(out_page);
+       workspace->out_buf.dst = kmap(out_page);
        workspace->out_buf.pos = 0;
        workspace->out_buf.size = min_t(size_t, max_out, PAGE_SIZE);
 
@@ -446,6 +446,7 @@ int zstd_compress_pages(struct list_head *ws, struct address_space *mapping,
                if (workspace->out_buf.pos == workspace->out_buf.size) {
                        tot_out += PAGE_SIZE;
                        max_out -= PAGE_SIZE;
+                       kunmap(out_page);
                        if (nr_pages == nr_dest_pages) {
                                out_page = NULL;
                                ret = -E2BIG;
@@ -457,7 +458,7 @@ int zstd_compress_pages(struct list_head *ws, struct address_space *mapping,
                                goto out;
                        }
                        pages[nr_pages++] = out_page;
-                       workspace->out_buf.dst = page_address(out_page);
+                       workspace->out_buf.dst = kmap(out_page);
                        workspace->out_buf.pos = 0;
                        workspace->out_buf.size = min_t(size_t, max_out,
                                                        PAGE_SIZE);
@@ -472,12 +473,13 @@ int zstd_compress_pages(struct list_head *ws, struct address_space *mapping,
                /* Check if we need more input */
                if (workspace->in_buf.pos == workspace->in_buf.size) {
                        tot_in += PAGE_SIZE;
+                       kunmap(in_page);
                        put_page(in_page);
 
                        start += PAGE_SIZE;
                        len -= PAGE_SIZE;
                        in_page = find_get_page(mapping, start >> PAGE_SHIFT);
-                       workspace->in_buf.src = page_address(in_page);
+                       workspace->in_buf.src = kmap(in_page);
                        workspace->in_buf.pos = 0;
                        workspace->in_buf.size = min_t(size_t, len, PAGE_SIZE);
                }
@@ -504,6 +506,7 @@ int zstd_compress_pages(struct list_head *ws, struct address_space *mapping,
 
                tot_out += PAGE_SIZE;
                max_out -= PAGE_SIZE;
+               kunmap(out_page);
                if (nr_pages == nr_dest_pages) {
                        out_page = NULL;
                        ret = -E2BIG;
@@ -515,7 +518,7 @@ int zstd_compress_pages(struct list_head *ws, struct address_space *mapping,
                        goto out;
                }
                pages[nr_pages++] = out_page;
-               workspace->out_buf.dst = page_address(out_page);
+               workspace->out_buf.dst = kmap(out_page);
                workspace->out_buf.pos = 0;
                workspace->out_buf.size = min_t(size_t, max_out, PAGE_SIZE);
        }
@@ -531,8 +534,12 @@ int zstd_compress_pages(struct list_head *ws, struct address_space *mapping,
 out:
        *out_pages = nr_pages;
        /* Cleanup */
-       if (in_page)
+       if (in_page) {
+               kunmap(in_page);
                put_page(in_page);
+       }
+       if (out_page)
+               kunmap(out_page);
        return ret;
 }
 
@@ -556,7 +563,7 @@ int zstd_decompress_bio(struct list_head *ws, struct compressed_bio *cb)
                goto done;
        }
 
-       workspace->in_buf.src = page_address(pages_in[page_in_index]);
+       workspace->in_buf.src = kmap(pages_in[page_in_index]);
        workspace->in_buf.pos = 0;
        workspace->in_buf.size = min_t(size_t, srclen, PAGE_SIZE);
 
@@ -592,14 +599,14 @@ int zstd_decompress_bio(struct list_head *ws, struct compressed_bio *cb)
                        break;
 
                if (workspace->in_buf.pos == workspace->in_buf.size) {
-                       page_in_index++;
+                       kunmap(pages_in[page_in_index++]);
                        if (page_in_index >= total_pages_in) {
                                workspace->in_buf.src = NULL;
                                ret = -EIO;
                                goto done;
                        }
                        srclen -= PAGE_SIZE;
-                       workspace->in_buf.src = page_address(pages_in[page_in_index]);
+                       workspace->in_buf.src = kmap(pages_in[page_in_index]);
                        workspace->in_buf.pos = 0;
                        workspace->in_buf.size = min_t(size_t, srclen, PAGE_SIZE);
                }
@@ -607,6 +614,8 @@ int zstd_decompress_bio(struct list_head *ws, struct compressed_bio *cb)
        ret = 0;
        zero_fill_bio(cb->orig_bio);
 done:
+       if (workspace->in_buf.src)
+               kunmap(pages_in[page_in_index]);
        return ret;
 }